sys/netpfil/pf/pf_norm.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright 2001 Niels Provos <provos@citi.umich.edu>
   5  * Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  *      $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $
  29  */
  30
  31 #include <sys/cdefs.h>
  32 __FBSDID("$FreeBSD$");
  33
  34 #include "opt_inet.h"
  35 #include "opt_inet6.h"
  36 #include "opt_pf.h"
  37
  38 #include <sys/param.h>
  39 #include <sys/kernel.h>
  40 #include <sys/lock.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/mutex.h>
  43 #include <sys/refcount.h>
  44 #include <sys/socket.h>
  45
  46 #include <net/if.h>
  47 #include <net/vnet.h>
  48 #include <net/pfvar.h>
  49 #include <net/if_pflog.h>
  50
  51 #include <netinet/in.h>
  52 #include <netinet/ip.h>
  53 #include <netinet/ip_var.h>
  54 #include <netinet6/ip6_var.h>
  55 #include <netinet/tcp.h>
  56 #include <netinet/tcp_fsm.h>
  57 #include <netinet/tcp_seq.h>
  58
  59 #ifdef INET6
  60 #include <netinet/ip6.h>
  61 #endif /* INET6 */
  62
  63 struct pf_frent {
  64         TAILQ_ENTRY(pf_frent)   fr_next;
  65         struct mbuf     *fe_m;
  66         uint16_t        fe_hdrlen;      /* ipv4 header length with ip options
  67                                            ipv6, extension, fragment header */
  68         uint16_t        fe_extoff;      /* last extension header offset or 0 */
  69         uint16_t        fe_len;         /* fragment length */
  70         uint16_t        fe_off;         /* fragment offset */
  71         uint16_t        fe_mff;         /* more fragment flag */
  72 };
  73
  74 struct pf_fragment_cmp {
  75         struct pf_addr  frc_src;
  76         struct pf_addr  frc_dst;
  77         uint32_t        frc_id;
  78         sa_family_t     frc_af;
  79         uint8_t         frc_proto;
  80 };
  81
  82 struct pf_fragment {
  83         struct pf_fragment_cmp  fr_key;
  84 #define fr_src  fr_key.frc_src
  85 #define fr_dst  fr_key.frc_dst
  86 #define fr_id   fr_key.frc_id
  87 #define fr_af   fr_key.frc_af
  88 #define fr_proto        fr_key.frc_proto
  89
  90         /* pointers to queue element */
  91         struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS];
  92         /* count entries between pointers */
  93         uint8_t fr_entries[PF_FRAG_ENTRY_POINTS];
  94         RB_ENTRY(pf_fragment) fr_entry;
  95         TAILQ_ENTRY(pf_fragment) frag_next;
  96         uint32_t        fr_timeout;
  97         uint16_t        fr_maxlen;      /* maximum length of single fragment */
  98         u_int16_t       fr_holes;       /* number of holes in the queue */
  99         TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
 100 };
 101
 102 struct pf_fragment_tag {
 103         uint16_t        ft_hdrlen;      /* header length of reassembled pkt */
 104         uint16_t        ft_extoff;      /* last extension header offset or 0 */
 105         uint16_t        ft_maxlen;      /* maximum fragment payload length */
 106         uint32_t        ft_id;          /* fragment id */
 107 };
 108
 109 VNET_DEFINE_STATIC(struct mtx, pf_frag_mtx);
 110 #define V_pf_frag_mtx           VNET(pf_frag_mtx)
 111 #define PF_FRAG_LOCK()          mtx_lock(&V_pf_frag_mtx)
 112 #define PF_FRAG_UNLOCK()        mtx_unlock(&V_pf_frag_mtx)
 113 #define PF_FRAG_ASSERT()        mtx_assert(&V_pf_frag_mtx, MA_OWNED)
 114
 115 VNET_DEFINE(uma_zone_t, pf_state_scrub_z);      /* XXX: shared with pfsync */
 116
 117 VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z);
 118 #define V_pf_frent_z    VNET(pf_frent_z)
 119 VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z);
 120 #define V_pf_frag_z     VNET(pf_frag_z)
 121
 122 TAILQ_HEAD(pf_fragqueue, pf_fragment);
 123 TAILQ_HEAD(pf_cachequeue, pf_fragment);
 124 VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue);
 125 #define V_pf_fragqueue                  VNET(pf_fragqueue)
 126 RB_HEAD(pf_frag_tree, pf_fragment);
 127 VNET_DEFINE_STATIC(struct pf_frag_tree, pf_frag_tree);
 128 #define V_pf_frag_tree                  VNET(pf_frag_tree)
 129 static int               pf_frag_compare(struct pf_fragment *,
 130                             struct pf_fragment *);
 131 static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
 132 static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
 133
 134 static void     pf_flush_fragments(void);
 135 static void     pf_free_fragment(struct pf_fragment *);
 136 static void     pf_remove_fragment(struct pf_fragment *);
 137 static int      pf_normalize_tcpopt(struct pf_rule *, struct mbuf *,
 138                     struct tcphdr *, int, sa_family_t);
 139 static struct pf_frent *pf_create_fragment(u_short *);
 140 static int      pf_frent_holes(struct pf_frent *frent);
 141 static struct pf_fragment *pf_find_fragment(struct pf_fragment_cmp *key,
 142                     struct pf_frag_tree *tree);
 143 static inline int       pf_frent_index(struct pf_frent *);
 144 static int      pf_frent_insert(struct pf_fragment *,
 145                             struct pf_frent *, struct pf_frent *);
 146 void                    pf_frent_remove(struct pf_fragment *,
 147                             struct pf_frent *);
 148 struct pf_frent         *pf_frent_previous(struct pf_fragment *,
 149                             struct pf_frent *);
 150 static struct pf_fragment *pf_fillup_fragment(struct pf_fragment_cmp *,
 151                     struct pf_frent *, u_short *);
 152 static struct mbuf *pf_join_fragment(struct pf_fragment *);
 153 #ifdef INET
 154 static void     pf_scrub_ip(struct mbuf **, uint32_t, uint8_t, uint8_t);
 155 static int      pf_reassemble(struct mbuf **, struct ip *, int, u_short *);
 156 #endif  /* INET */
 157 #ifdef INET6
 158 static int      pf_reassemble6(struct mbuf **, struct ip6_hdr *,
 159                     struct ip6_frag *, uint16_t, uint16_t, u_short *);
 160 static void     pf_scrub_ip6(struct mbuf **, uint8_t);
 161 #endif  /* INET6 */
 162
 163 #define DPFPRINTF(x) do {                               \
 164         if (V_pf_status.debug >= PF_DEBUG_MISC) {       \
 165                 printf("%s: ", __func__);               \
 166                 printf x ;                              \
 167         }                                               \
 168 } while(0)
 169
 170 #ifdef INET
 171 static void
 172 pf_ip2key(struct ip *ip, int dir, struct pf_fragment_cmp *key)
 173 {
 174
 175         key->frc_src.v4 = ip->ip_src;
 176         key->frc_dst.v4 = ip->ip_dst;
 177         key->frc_af = AF_INET;
 178         key->frc_proto = ip->ip_p;
 179         key->frc_id = ip->ip_id;
 180 }
 181 #endif  /* INET */
 182
 183 void
 184 pf_normalize_init(void)
 185 {
 186
 187         V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment),
 188             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 189         V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent),
 190             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 191         V_pf_state_scrub_z = uma_zcreate("pf state scrubs",
 192             sizeof(struct pf_state_scrub),  NULL, NULL, NULL, NULL,
 193             UMA_ALIGN_PTR, 0);
 194
 195         mtx_init(&V_pf_frag_mtx, "pf fragments", NULL, MTX_DEF);
 196
 197         V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z;
 198         V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT;
 199         uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT);
 200         uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached");
 201
 202         TAILQ_INIT(&V_pf_fragqueue);
 203 }
 204
 205 void
 206 pf_normalize_cleanup(void)
 207 {
 208
 209         uma_zdestroy(V_pf_state_scrub_z);
 210         uma_zdestroy(V_pf_frent_z);
 211         uma_zdestroy(V_pf_frag_z);
 212
 213         mtx_destroy(&V_pf_frag_mtx);
 214 }
 215
 216 static int
 217 pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
 218 {
 219         int     diff;
 220
 221         if ((diff = a->fr_id - b->fr_id) != 0)
 222                 return (diff);
 223         if ((diff = a->fr_proto - b->fr_proto) != 0)
 224                 return (diff);
 225         if ((diff = a->fr_af - b->fr_af) != 0)
 226                 return (diff);
 227         if ((diff = pf_addr_cmp(&a->fr_src, &b->fr_src, a->fr_af)) != 0)
 228                 return (diff);
 229         if ((diff = pf_addr_cmp(&a->fr_dst, &b->fr_dst, a->fr_af)) != 0)
 230                 return (diff);
 231         return (0);
 232 }
 233
 234 void
 235 pf_purge_expired_fragments(void)
 236 {
 237         u_int32_t       expire = time_uptime -
 238                             V_pf_default_rule.timeout[PFTM_FRAG];
 239
 240         pf_purge_fragments(expire);
 241 }
 242
 243 void
 244 pf_purge_fragments(uint32_t expire)
 245 {
 246         struct pf_fragment      *frag;
 247
 248         PF_FRAG_LOCK();
 249         while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
 250                 if (frag->fr_timeout > expire)
 251                         break;
 252
 253                 DPFPRINTF(("expiring %d(%p)\n", frag->fr_id, frag));
 254                 pf_free_fragment(frag);
 255         }
 256
 257         PF_FRAG_UNLOCK();
 258 }
 259
 260 /*
 261  * Try to flush old fragments to make space for new ones
 262  */
 263 static void
 264 pf_flush_fragments(void)
 265 {
 266         struct pf_fragment      *frag;
 267         int                      goal;
 268
 269         PF_FRAG_ASSERT();
 270
 271         goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10;
 272         DPFPRINTF(("trying to free %d frag entriess\n", goal));
 273         while (goal < uma_zone_get_cur(V_pf_frent_z)) {
 274                 frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue);
 275                 if (frag)
 276                         pf_free_fragment(frag);
 277                 else
 278                         break;
 279         }
 280 }
 281
 282 /* Frees the fragments and all associated entries */
 283 static void
 284 pf_free_fragment(struct pf_fragment *frag)
 285 {
 286         struct pf_frent         *frent;
 287
 288         PF_FRAG_ASSERT();
 289
 290         /* Free all fragments */
 291         for (frent = TAILQ_FIRST(&frag->fr_queue); frent;
 292             frent = TAILQ_FIRST(&frag->fr_queue)) {
 293                 TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
 294
 295                 m_freem(frent->fe_m);
 296                 uma_zfree(V_pf_frent_z, frent);
 297         }
 298
 299         pf_remove_fragment(frag);
 300 }
 301
 302 static struct pf_fragment *
 303 pf_find_fragment(struct pf_fragment_cmp *key, struct pf_frag_tree *tree)
 304 {
 305         struct pf_fragment      *frag;
 306
 307         PF_FRAG_ASSERT();
 308
 309         frag = RB_FIND(pf_frag_tree, tree, (struct pf_fragment *)key);
 310         if (frag != NULL) {
 311                 /* XXX Are we sure we want to update the timeout? */
 312                 frag->fr_timeout = time_uptime;
 313                 TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
 314                 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
 315         }
 316
 317         return (frag);
 318 }
 319
 320 /* Removes a fragment from the fragment queue and frees the fragment */
 321 static void
 322 pf_remove_fragment(struct pf_fragment *frag)
 323 {
 324
 325         PF_FRAG_ASSERT();
 326         KASSERT(frag, ("frag != NULL"));
 327
 328         RB_REMOVE(pf_frag_tree, &V_pf_frag_tree, frag);
 329         TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
 330         uma_zfree(V_pf_frag_z, frag);
 331 }
 332
 333 static struct pf_frent *
 334 pf_create_fragment(u_short *reason)
 335 {
 336         struct pf_frent *frent;
 337
 338         PF_FRAG_ASSERT();
 339
 340         frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
 341         if (frent == NULL) {
 342                 pf_flush_fragments();
 343                 frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
 344                 if (frent == NULL) {
 345                         REASON_SET(reason, PFRES_MEMORY);
 346                         return (NULL);
 347                 }
 348         }
 349
 350         return (frent);
 351 }
 352
 353 /*
 354  * Calculate the additional holes that were created in the fragment
 355  * queue by inserting this fragment.  A fragment in the middle
 356  * creates one more hole by splitting.  For each connected side,
 357  * it loses one hole.
 358  * Fragment entry must be in the queue when calling this function.
 359  */
 360 static int
 361 pf_frent_holes(struct pf_frent *frent)
 362 {
 363         struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
 364         struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
 365         int holes = 1;
 366
 367         if (prev == NULL) {
 368                 if (frent->fe_off == 0)
 369                         holes--;
 370         } else {
 371                 KASSERT(frent->fe_off != 0, ("frent->fe_off != 0"));
 372                 if (frent->fe_off == prev->fe_off + prev->fe_len)
 373                         holes--;
 374         }
 375         if (next == NULL) {
 376                 if (!frent->fe_mff)
 377                         holes--;
 378         } else {
 379                 KASSERT(frent->fe_mff, ("frent->fe_mff"));
 380                 if (next->fe_off == frent->fe_off + frent->fe_len)
 381                         holes--;
 382         }
 383         return holes;
 384 }
 385
 386 static inline int
 387 pf_frent_index(struct pf_frent *frent)
 388 {
 389         /*
 390          * We have an array of 16 entry points to the queue.  A full size
 391          * 65535 octet IP packet can have 8192 fragments.  So the queue
 392          * traversal length is at most 512 and at most 16 entry points are
 393          * checked.  We need 128 additional bytes on a 64 bit architecture.
 394          */
 395         CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) ==
 396             16 - 1);
 397         CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1);
 398
 399         return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS);
 400 }
 401
 402 static int
 403 pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent,
 404     struct pf_frent *prev)
 405 {
 406         int index;
 407
 408         CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff);
 409
 410         /*
 411          * A packet has at most 65536 octets.  With 16 entry points, each one
 412          * spawns 4096 octets.  We limit these to 64 fragments each, which
 413          * means on average every fragment must have at least 64 octets.
 414          */
 415         index = pf_frent_index(frent);
 416         if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT)
 417                 return ENOBUFS;
 418         frag->fr_entries[index]++;
 419
 420         if (prev == NULL) {
 421                 TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
 422         } else {
 423                 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
 424                     ("overlapping fragment"));
 425                 TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
 426         }
 427
 428         if (frag->fr_firstoff[index] == NULL) {
 429                 KASSERT(prev == NULL || pf_frent_index(prev) < index,
 430                     ("prev == NULL || pf_frent_index(pref) < index"));
 431                 frag->fr_firstoff[index] = frent;
 432         } else {
 433                 if (frent->fe_off < frag->fr_firstoff[index]->fe_off) {
 434                         KASSERT(prev == NULL || pf_frent_index(prev) < index,
 435                             ("prev == NULL || pf_frent_index(pref) < index"));
 436                         frag->fr_firstoff[index] = frent;
 437                 } else {
 438                         KASSERT(prev != NULL, ("prev != NULL"));
 439                         KASSERT(pf_frent_index(prev) == index,
 440                             ("pf_frent_index(prev) == index"));
 441                 }
 442         }
 443
 444         frag->fr_holes += pf_frent_holes(frent);
 445
 446         return 0;
 447 }
 448
 449 void
 450 pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent)
 451 {
 452 #ifdef INVARIANTS
 453         struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
 454 #endif
 455         struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
 456         int index;
 457
 458         frag->fr_holes -= pf_frent_holes(frent);
 459
 460         index = pf_frent_index(frent);
 461         KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found"));
 462         if (frag->fr_firstoff[index]->fe_off == frent->fe_off) {
 463                 if (next == NULL) {
 464                         frag->fr_firstoff[index] = NULL;
 465                 } else {
 466                         KASSERT(frent->fe_off + frent->fe_len <= next->fe_off,
 467                             ("overlapping fragment"));
 468                         if (pf_frent_index(next) == index) {
 469                                 frag->fr_firstoff[index] = next;
 470                         } else {
 471                                 frag->fr_firstoff[index] = NULL;
 472                         }
 473                 }
 474         } else {
 475                 KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off,
 476                     ("frag->fr_firstoff[index]->fe_off < frent->fe_off"));
 477                 KASSERT(prev != NULL, ("prev != NULL"));
 478                 KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
 479                     ("overlapping fragment"));
 480                 KASSERT(pf_frent_index(prev) == index,
 481                     ("pf_frent_index(prev) == index"));
 482         }
 483
 484         TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
 485
 486         KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining"));
 487         frag->fr_entries[index]--;
 488 }
 489
 490 struct pf_frent *
 491 pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent)
 492 {
 493         struct pf_frent *prev, *next;
 494         int index;
 495
 496         /*
 497          * If there are no fragments after frag, take the final one.  Assume
 498          * that the global queue is not empty.
 499          */
 500         prev = TAILQ_LAST(&frag->fr_queue, pf_fragq);
 501         KASSERT(prev != NULL, ("prev != NULL"));
 502         if (prev->fe_off <= frent->fe_off)
 503                 return prev;
 504         /*
 505          * We want to find a fragment entry that is before frag, but still
 506          * close to it.  Find the first fragment entry that is in the same
 507          * entry point or in the first entry point after that.  As we have
 508          * already checked that there are entries behind frag, this will
 509          * succeed.
 510          */
 511         for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS;
 512             index++) {
 513                 prev = frag->fr_firstoff[index];
 514                 if (prev != NULL)
 515                         break;
 516         }
 517         KASSERT(prev != NULL, ("prev != NULL"));
 518         /*
 519          * In prev we may have a fragment from the same entry point that is
 520          * before frent, or one that is just one position behind frent.
 521          * In the latter case, we go back one step and have the predecessor.
 522          * There may be none if the new fragment will be the first one.
 523          */
 524         if (prev->fe_off > frent->fe_off) {
 525                 prev = TAILQ_PREV(prev, pf_fragq, fr_next);
 526                 if (prev == NULL)
 527                         return NULL;
 528                 KASSERT(prev->fe_off <= frent->fe_off,
 529                     ("prev->fe_off <= frent->fe_off"));
 530                 return prev;
 531         }
 532         /*
 533          * In prev is the first fragment of the entry point.  The offset
 534          * of frag is behind it.  Find the closest previous fragment.
 535          */
 536         for (next = TAILQ_NEXT(prev, fr_next); next != NULL;
 537             next = TAILQ_NEXT(next, fr_next)) {
 538                 if (next->fe_off > frent->fe_off)
 539                         break;
 540                 prev = next;
 541         }
 542         return prev;
 543 }
 544
 545 static struct pf_fragment *
 546 pf_fillup_fragment(struct pf_fragment_cmp *key, struct pf_frent *frent,
 547     u_short *reason)
 548 {
 549         struct pf_frent         *after, *next, *prev;
 550         struct pf_fragment      *frag;
 551         uint16_t                total;
 552
 553         PF_FRAG_ASSERT();
 554
 555         /* No empty fragments. */
 556         if (frent->fe_len == 0) {
 557                 DPFPRINTF(("bad fragment: len 0\n"));
 558                 goto bad_fragment;
 559         }
 560
 561         /* All fragments are 8 byte aligned. */
 562         if (frent->fe_mff && (frent->fe_len & 0x7)) {
 563                 DPFPRINTF(("bad fragment: mff and len %d\n", frent->fe_len));
 564                 goto bad_fragment;
 565         }
 566
 567         /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */
 568         if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
 569                 DPFPRINTF(("bad fragment: max packet %d\n",
 570                     frent->fe_off + frent->fe_len));
 571                 goto bad_fragment;
 572         }
 573
 574         DPFPRINTF((key->frc_af == AF_INET ?
 575             "reass frag %d @ %d-%d\n" : "reass frag %#08x @ %d-%d\n",
 576             key->frc_id, frent->fe_off, frent->fe_off + frent->fe_len));
 577
 578         /* Fully buffer all of the fragments in this fragment queue. */
 579         frag = pf_find_fragment(key, &V_pf_frag_tree);
 580
 581         /* Create a new reassembly queue for this packet. */
 582         if (frag == NULL) {
 583                 frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
 584                 if (frag == NULL) {
 585                         pf_flush_fragments();
 586                         frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
 587                         if (frag == NULL) {
 588                                 REASON_SET(reason, PFRES_MEMORY);
 589                                 goto drop_fragment;
 590                         }
 591                 }
 592
 593                 *(struct pf_fragment_cmp *)frag = *key;
 594                 memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff));
 595                 memset(frag->fr_entries, 0, sizeof(frag->fr_entries));
 596                 frag->fr_timeout = time_uptime;
 597                 frag->fr_maxlen = frent->fe_len;
 598                 frag->fr_holes = 1;
 599                 TAILQ_INIT(&frag->fr_queue);
 600
 601                 RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
 602                 TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);
 603
 604                 /* We do not have a previous fragment, cannot fail. */
 605                 pf_frent_insert(frag, frent, NULL);
 606
 607                 return (frag);
 608         }
 609
 610         KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
 611
 612         /* Remember maximum fragment len for refragmentation. */
 613         if (frent->fe_len > frag->fr_maxlen)
 614                 frag->fr_maxlen = frent->fe_len;
 615
 616         /* Maximum data we have seen already. */
 617         total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
 618                 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
 619
 620         /* Non terminal fragments must have more fragments flag. */
 621         if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
 622                 goto bad_fragment;
 623
 624         /* Check if we saw the last fragment already. */
 625         if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
 626                 if (frent->fe_off + frent->fe_len > total ||
 627                     (frent->fe_off + frent->fe_len == total && frent->fe_mff))
 628                         goto bad_fragment;
 629         } else {
 630                 if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
 631                         goto bad_fragment;
 632         }
 633
 634         /* Find neighbors for newly inserted fragment */
 635         prev = pf_frent_previous(frag, frent);
 636         if (prev == NULL) {
 637                 after = TAILQ_FIRST(&frag->fr_queue);
 638                 KASSERT(after != NULL, ("after != NULL"));
 639         } else {
 640                 after = TAILQ_NEXT(prev, fr_next);
 641         }
 642
 643         if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
 644                 uint16_t precut;
 645
 646                 precut = prev->fe_off + prev->fe_len - frent->fe_off;
 647                 if (precut >= frent->fe_len)
 648                         goto bad_fragment;
 649                 DPFPRINTF(("overlap -%d\n", precut));
 650                 m_adj(frent->fe_m, precut);
 651                 frent->fe_off += precut;
 652                 frent->fe_len -= precut;
 653         }
 654
 655         for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
 656             after = next) {
 657                 uint16_t aftercut;
 658
 659                 aftercut = frent->fe_off + frent->fe_len - after->fe_off;
 660                 DPFPRINTF(("adjust overlap %d\n", aftercut));
 661                 if (aftercut < after->fe_len) {
 662                         m_adj(after->fe_m, aftercut);
 663                         after->fe_off += aftercut;
 664                         after->fe_len -= aftercut;
 665                         break;
 666                 }
 667
 668                 /* This fragment is completely overlapped, lose it. */
 669                 next = TAILQ_NEXT(after, fr_next);
 670                 pf_frent_remove(frag, after);
 671                 m_freem(after->fe_m);
 672                 uma_zfree(V_pf_frent_z, after);
 673         }
 674
 675         /* If part of the queue gets too long, there is not way to recover. */
 676         if (pf_frent_insert(frag, frent, prev)) {
 677                 DPFPRINTF(("fragment queue limit exceeded\n"));
 678                 goto bad_fragment;
 679         }
 680
 681         return (frag);
 682
 683 bad_fragment:
 684         REASON_SET(reason, PFRES_FRAG);
 685 drop_fragment:
 686         uma_zfree(V_pf_frent_z, frent);
 687         return (NULL);
 688 }
 689
 690 static struct mbuf *
 691 pf_join_fragment(struct pf_fragment *frag)
 692 {
 693         struct mbuf *m, *m2;
 694         struct pf_frent *frent, *next;
 695
 696         frent = TAILQ_FIRST(&frag->fr_queue);
 697         next = TAILQ_NEXT(frent, fr_next);
 698
 699         m = frent->fe_m;
 700         m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
 701         uma_zfree(V_pf_frent_z, frent);
 702         for (frent = next; frent != NULL; frent = next) {
 703                 next = TAILQ_NEXT(frent, fr_next);
 704
 705                 m2 = frent->fe_m;
 706                 /* Strip off ip header. */
 707                 m_adj(m2, frent->fe_hdrlen);
 708                 /* Strip off any trailing bytes. */
 709                 m_adj(m2, frent->fe_len - m2->m_pkthdr.len);
 710
 711                 uma_zfree(V_pf_frent_z, frent);
 712                 m_cat(m, m2);
 713         }
 714
 715         /* Remove from fragment queue. */
 716         pf_remove_fragment(frag);
 717
 718         return (m);
 719 }
 720
 721 #ifdef INET
 722 static int
 723 pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason)
 724 {
 725         struct mbuf             *m = *m0;
 726         struct pf_frent         *frent;
 727         struct pf_fragment      *frag;
 728         struct pf_fragment_cmp  key;
 729         uint16_t                total, hdrlen;
 730
 731         /* Get an entry for the fragment queue */
 732         if ((frent = pf_create_fragment(reason)) == NULL)
 733                 return (PF_DROP);
 734
 735         frent->fe_m = m;
 736         frent->fe_hdrlen = ip->ip_hl << 2;
 737         frent->fe_extoff = 0;
 738         frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
 739         frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
 740         frent->fe_mff = ntohs(ip->ip_off) & IP_MF;
 741
 742         pf_ip2key(ip, dir, &key);
 743
 744         if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL)
 745                 return (PF_DROP);
 746
 747         /* The mbuf is part of the fragment entry, no direct free or access */
 748         m = *m0 = NULL;
 749
 750         if (frag->fr_holes) {
 751                 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id, frag->fr_holes));
 752                 return (PF_PASS);  /* drop because *m0 is NULL, no error */
 753         }
 754
 755         /* We have all the data */
 756         frent = TAILQ_FIRST(&frag->fr_queue);
 757         KASSERT(frent != NULL, ("frent != NULL"));
 758         total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
 759                 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
 760         hdrlen = frent->fe_hdrlen;
 761
 762         m = *m0 = pf_join_fragment(frag);
 763         frag = NULL;
 764
 765         if (m->m_flags & M_PKTHDR) {
 766                 int plen = 0;
 767                 for (m = *m0; m; m = m->m_next)
 768                         plen += m->m_len;
 769                 m = *m0;
 770                 m->m_pkthdr.len = plen;
 771         }
 772
 773         ip = mtod(m, struct ip *);
 774         ip->ip_len = htons(hdrlen + total);
 775         ip->ip_off &= ~(IP_MF|IP_OFFMASK);
 776
 777         if (hdrlen + total > IP_MAXPACKET) {
 778                 DPFPRINTF(("drop: too big: %d\n", total));
 779                 ip->ip_len = 0;
 780                 REASON_SET(reason, PFRES_SHORT);
 781                 /* PF_DROP requires a valid mbuf *m0 in pf_test() */
 782                 return (PF_DROP);
 783         }
 784
 785         DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip->ip_len)));
 786         return (PF_PASS);
 787 }
 788 #endif  /* INET */
 789
 790 #ifdef INET6
 791 static int
 792 pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr,
 793     uint16_t hdrlen, uint16_t extoff, u_short *reason)
 794 {
 795         struct mbuf             *m = *m0;
 796         struct pf_frent         *frent;
 797         struct pf_fragment      *frag;
 798         struct pf_fragment_cmp   key;
 799         struct m_tag            *mtag;
 800         struct pf_fragment_tag  *ftag;
 801         int                      off;
 802         uint32_t                 frag_id;
 803         uint16_t                 total, maxlen;
 804         uint8_t                  proto;
 805
 806         PF_FRAG_LOCK();
 807
 808         /* Get an entry for the fragment queue. */
 809         if ((frent = pf_create_fragment(reason)) == NULL) {
 810                 PF_FRAG_UNLOCK();
 811                 return (PF_DROP);
 812         }
 813
 814         frent->fe_m = m;
 815         frent->fe_hdrlen = hdrlen;
 816         frent->fe_extoff = extoff;
 817         frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen;
 818         frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK);
 819         frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG;
 820
 821         key.frc_src.v6 = ip6->ip6_src;
 822         key.frc_dst.v6 = ip6->ip6_dst;
 823         key.frc_af = AF_INET6;
 824         /* Only the first fragment's protocol is relevant. */
 825         key.frc_proto = 0;
 826         key.frc_id = fraghdr->ip6f_ident;
 827
 828         if ((frag = pf_fillup_fragment(&key, frent, reason)) == NULL) {
 829                 PF_FRAG_UNLOCK();
 830                 return (PF_DROP);
 831         }
 832
 833         /* The mbuf is part of the fragment entry, no direct free or access. */
 834         m = *m0 = NULL;
 835
 836         if (frag->fr_holes) {
 837                 DPFPRINTF(("frag %d, holes %d\n", frag->fr_id,
 838                     frag->fr_holes));
 839                 PF_FRAG_UNLOCK();
 840                 return (PF_PASS);  /* Drop because *m0 is NULL, no error. */
 841         }
 842
 843         /* We have all the data. */
 844         frent = TAILQ_FIRST(&frag->fr_queue);
 845         KASSERT(frent != NULL, ("frent != NULL"));
 846         extoff = frent->fe_extoff;
 847         maxlen = frag->fr_maxlen;
 848         frag_id = frag->fr_id;
 849         total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
 850                 TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
 851         hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);
 852
 853         m = *m0 = pf_join_fragment(frag);
 854         frag = NULL;
 855
 856         PF_FRAG_UNLOCK();
 857
 858         /* Take protocol from first fragment header. */
 859         m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off);
 860         KASSERT(m, ("%s: short mbuf chain", __func__));
 861         proto = *(mtod(m, caddr_t) + off);
 862         m = *m0;
 863
 864         /* Delete frag6 header */
 865         if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0)
 866                 goto fail;
 867
 868         if (m->m_flags & M_PKTHDR) {
 869                 int plen = 0;
 870                 for (m = *m0; m; m = m->m_next)
 871                         plen += m->m_len;
 872                 m = *m0;
 873                 m->m_pkthdr.len = plen;
 874         }
 875
 876         if ((mtag = m_tag_get(PF_REASSEMBLED, sizeof(struct pf_fragment_tag),
 877             M_NOWAIT)) == NULL)
 878                 goto fail;
 879         ftag = (struct pf_fragment_tag *)(mtag + 1);
 880         ftag->ft_hdrlen = hdrlen;
 881         ftag->ft_extoff = extoff;
 882         ftag->ft_maxlen = maxlen;
 883         ftag->ft_id = frag_id;
 884         m_tag_prepend(m, mtag);
 885
 886         ip6 = mtod(m, struct ip6_hdr *);
 887         ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
 888         if (extoff) {
 889                 /* Write protocol into next field of last extension header. */
 890                 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
 891                     &off);
 892                 KASSERT(m, ("%s: short mbuf chain", __func__));
 893                 *(mtod(m, char *) + off) = proto;
 894                 m = *m0;
 895         } else
 896                 ip6->ip6_nxt = proto;
 897
 898         if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
 899                 DPFPRINTF(("drop: too big: %d\n", total));
 900                 ip6->ip6_plen = 0;
 901                 REASON_SET(reason, PFRES_SHORT);
 902                 /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */
 903                 return (PF_DROP);
 904         }
 905
 906         DPFPRINTF(("complete: %p(%d)\n", m, ntohs(ip6->ip6_plen)));
 907         return (PF_PASS);
 908
 909 fail:
 910         REASON_SET(reason, PFRES_MEMORY);
 911         /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */
 912         return (PF_DROP);
 913 }
 914 #endif  /* INET6 */
 915
 916 #ifdef INET6
 917 int
 918 pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag)
 919 {
 920         struct mbuf             *m = *m0, *t;
 921         struct pf_fragment_tag  *ftag = (struct pf_fragment_tag *)(mtag + 1);
 922         struct pf_pdesc          pd;
 923         uint32_t                 frag_id;
 924         uint16_t                 hdrlen, extoff, maxlen;
 925         uint8_t                  proto;
 926         int                      error, action;
 927
 928         hdrlen = ftag->ft_hdrlen;
 929         extoff = ftag->ft_extoff;
 930         maxlen = ftag->ft_maxlen;
 931         frag_id = ftag->ft_id;
 932         m_tag_delete(m, mtag);
 933         mtag = NULL;
 934         ftag = NULL;
 935
 936         if (extoff) {
 937                 int off;
 938
 939                 /* Use protocol from next field of last extension header */
 940                 m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
 941                     &off);
 942                 KASSERT((m != NULL), ("pf_refragment6: short mbuf chain"));
 943                 proto = *(mtod(m, caddr_t) + off);
 944                 *(mtod(m, char *) + off) = IPPROTO_FRAGMENT;
 945                 m = *m0;
 946         } else {
 947                 struct ip6_hdr *hdr;
 948
 949                 hdr = mtod(m, struct ip6_hdr *);
 950                 proto = hdr->ip6_nxt;
 951                 hdr->ip6_nxt = IPPROTO_FRAGMENT;
 952         }
 953
 954         /* The MTU must be a multiple of 8 bytes, or we risk doing the
 955          * fragmentation wrong. */
 956         maxlen = maxlen & ~7;
 957
 958         /*
 959          * Maxlen may be less than 8 if there was only a single
 960          * fragment.  As it was fragmented before, add a fragment
 961          * header also for a single fragment.  If total or maxlen
 962          * is less than 8, ip6_fragment() will return EMSGSIZE and
 963          * we drop the packet.
 964          */
 965         error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
 966         m = (*m0)->m_nextpkt;
 967         (*m0)->m_nextpkt = NULL;
 968         if (error == 0) {
 969                 /* The first mbuf contains the unfragmented packet. */
 970                 m_freem(*m0);
 971                 *m0 = NULL;
 972                 action = PF_PASS;
 973         } else {
 974                 /* Drop expects an mbuf to free. */
 975                 DPFPRINTF(("refragment error %d\n", error));
 976                 action = PF_DROP;
 977         }
 978         for (t = m; m; m = t) {
 979                 t = m->m_nextpkt;
 980                 m->m_nextpkt = NULL;
 981                 m->m_flags |= M_SKIP_FIREWALL;
 982                 memset(&pd, 0, sizeof(pd));
 983                 pd.pf_mtag = pf_find_mtag(m);
 984                 if (error == 0)
 985                         ip6_forward(m, 0);
 986                 else
 987                         m_freem(m);
 988         }
 989
 990         return (action);
 991 }
 992 #endif /* INET6 */
 993
 994 #ifdef INET
 995 int
 996 pf_normalize_ip(struct mbuf **m0, int dir, struct pfi_kif *kif, u_short *reason,
 997     struct pf_pdesc *pd)
 998 {
 999         struct mbuf             *m = *m0;
1000         struct pf_rule          *r;
1001         struct ip               *h = mtod(m, struct ip *);
1002         int                      mff = (ntohs(h->ip_off) & IP_MF);
1003         int                      hlen = h->ip_hl << 2;
1004         u_int16_t                fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
1005         u_int16_t                max;
1006         int                      ip_len;
1007         int                      ip_off;
1008         int                      tag = -1;
1009         int                      verdict;
1010
1011         PF_RULES_RASSERT();
1012
1013         r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1014         while (r != NULL) {
1015                 r->evaluations++;
1016                 if (pfi_kif_match(r->kif, kif) == r->ifnot)
1017                         r = r->skip[PF_SKIP_IFP].ptr;
1018                 else if (r->direction && r->direction != dir)
1019                         r = r->skip[PF_SKIP_DIR].ptr;
1020                 else if (r->af && r->af != AF_INET)
1021                         r = r->skip[PF_SKIP_AF].ptr;
1022                 else if (r->proto && r->proto != h->ip_p)
1023                         r = r->skip[PF_SKIP_PROTO].ptr;
1024                 else if (PF_MISMATCHAW(&r->src.addr,
1025                     (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
1026                     r->src.neg, kif, M_GETFIB(m)))
1027                         r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1028                 else if (PF_MISMATCHAW(&r->dst.addr,
1029                     (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
1030                     r->dst.neg, NULL, M_GETFIB(m)))
1031                         r = r->skip[PF_SKIP_DST_ADDR].ptr;
1032                 else if (r->match_tag && !pf_match_tag(m, r, &tag,
1033                     pd->pf_mtag ? pd->pf_mtag->tag : 0))
1034                         r = TAILQ_NEXT(r, entries);
1035                 else
1036                         break;
1037         }
1038
1039         if (r == NULL || r->action == PF_NOSCRUB)
1040                 return (PF_PASS);
1041         else {
1042                 r->packets[dir == PF_OUT]++;
1043                 r->bytes[dir == PF_OUT] += pd->tot_len;
1044         }
1045
1046         /* Check for illegal packets */
1047         if (hlen < (int)sizeof(struct ip)) {
1048                 REASON_SET(reason, PFRES_NORM);
1049                 goto drop;
1050         }
1051
1052         if (hlen > ntohs(h->ip_len)) {
1053                 REASON_SET(reason, PFRES_NORM);
1054                 goto drop;
1055         }
1056
1057         /* Clear IP_DF if the rule uses the no-df option */
1058         if (r->rule_flag & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
1059                 u_int16_t ip_off = h->ip_off;
1060
1061                 h->ip_off &= htons(~IP_DF);
1062                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1063         }
1064
1065         /* We will need other tests here */
1066         if (!fragoff && !mff)
1067                 goto no_fragment;
1068
1069         /* We're dealing with a fragment now. Don't allow fragments
1070          * with IP_DF to enter the cache. If the flag was cleared by
1071          * no-df above, fine. Otherwise drop it.
1072          */
1073         if (h->ip_off & htons(IP_DF)) {
1074                 DPFPRINTF(("IP_DF\n"));
1075                 goto bad;
1076         }
1077
1078         ip_len = ntohs(h->ip_len) - hlen;
1079         ip_off = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
1080
1081         /* All fragments are 8 byte aligned */
1082         if (mff && (ip_len & 0x7)) {
1083                 DPFPRINTF(("mff and %d\n", ip_len));
1084                 goto bad;
1085         }
1086
1087         /* Respect maximum length */
1088         if (fragoff + ip_len > IP_MAXPACKET) {
1089                 DPFPRINTF(("max packet %d\n", fragoff + ip_len));
1090                 goto bad;
1091         }
1092         max = fragoff + ip_len;
1093
1094         /* Fully buffer all of the fragments
1095          * Might return a completely reassembled mbuf, or NULL */
1096         PF_FRAG_LOCK();
1097         DPFPRINTF(("reass frag %d @ %d-%d\n", h->ip_id, fragoff, max));
1098         verdict = pf_reassemble(m0, h, dir, reason);
1099         PF_FRAG_UNLOCK();
1100
1101         if (verdict != PF_PASS)
1102                 return (PF_DROP);
1103
1104         m = *m0;
1105         if (m == NULL)
1106                 return (PF_DROP);
1107
1108         h = mtod(m, struct ip *);
1109
1110  no_fragment:
1111         /* At this point, only IP_DF is allowed in ip_off */
1112         if (h->ip_off & ~htons(IP_DF)) {
1113                 u_int16_t ip_off = h->ip_off;
1114
1115                 h->ip_off &= htons(IP_DF);
1116                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1117         }
1118
1119         pf_scrub_ip(&m, r->rule_flag, r->min_ttl, r->set_tos);
1120
1121         return (PF_PASS);
1122
1123  bad:
1124         DPFPRINTF(("dropping bad fragment\n"));
1125         REASON_SET(reason, PFRES_FRAG);
1126  drop:
1127         if (r != NULL && r->log)
1128                 PFLOG_PACKET(kif, m, AF_INET, dir, *reason, r, NULL, NULL, pd,
1129                     1);
1130
1131         return (PF_DROP);
1132 }
1133 #endif
1134
1135 #ifdef INET6
1136 int
1137 pf_normalize_ip6(struct mbuf **m0, int dir, struct pfi_kif *kif,
1138     u_short *reason, struct pf_pdesc *pd)
1139 {
1140         struct mbuf             *m = *m0;
1141         struct pf_rule          *r;
1142         struct ip6_hdr          *h = mtod(m, struct ip6_hdr *);
1143         int                      extoff;
1144         int                      off;
1145         struct ip6_ext           ext;
1146         struct ip6_opt           opt;
1147         struct ip6_frag          frag;
1148         u_int32_t                plen;
1149         int                      optend;
1150         int                      ooff;
1151         u_int8_t                 proto;
1152         int                      terminal;
1153
1154         PF_RULES_RASSERT();
1155
1156         r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1157         while (r != NULL) {
1158                 r->evaluations++;
1159                 if (pfi_kif_match(r->kif, kif) == r->ifnot)
1160                         r = r->skip[PF_SKIP_IFP].ptr;
1161                 else if (r->direction && r->direction != dir)
1162                         r = r->skip[PF_SKIP_DIR].ptr;
1163                 else if (r->af && r->af != AF_INET6)
1164                         r = r->skip[PF_SKIP_AF].ptr;
1165 #if 0 /* header chain! */
1166                 else if (r->proto && r->proto != h->ip6_nxt)
1167                         r = r->skip[PF_SKIP_PROTO].ptr;
1168 #endif
1169                 else if (PF_MISMATCHAW(&r->src.addr,
1170                     (struct pf_addr *)&h->ip6_src, AF_INET6,
1171                     r->src.neg, kif, M_GETFIB(m)))
1172                         r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1173                 else if (PF_MISMATCHAW(&r->dst.addr,
1174                     (struct pf_addr *)&h->ip6_dst, AF_INET6,
1175                     r->dst.neg, NULL, M_GETFIB(m)))
1176                         r = r->skip[PF_SKIP_DST_ADDR].ptr;
1177                 else
1178                         break;
1179         }
1180
1181         if (r == NULL || r->action == PF_NOSCRUB)
1182                 return (PF_PASS);
1183         else {
1184                 r->packets[dir == PF_OUT]++;
1185                 r->bytes[dir == PF_OUT] += pd->tot_len;
1186         }
1187
1188         /* Check for illegal packets */
1189         if (sizeof(struct ip6_hdr) + IPV6_MAXPACKET < m->m_pkthdr.len)
1190                 goto drop;
1191
1192         plen = ntohs(h->ip6_plen);
1193         /* jumbo payload option not supported */
1194         if (plen == 0)
1195                 goto drop;
1196
1197         extoff = 0;
1198         off = sizeof(struct ip6_hdr);
1199         proto = h->ip6_nxt;
1200         terminal = 0;
1201         do {
1202                 switch (proto) {
1203                 case IPPROTO_FRAGMENT:
1204                         goto fragment;
1205                         break;
1206                 case IPPROTO_AH:
1207                 case IPPROTO_ROUTING:
1208                 case IPPROTO_DSTOPTS:
1209                         if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1210                             NULL, AF_INET6))
1211                                 goto shortpkt;
1212                         extoff = off;
1213                         if (proto == IPPROTO_AH)
1214                                 off += (ext.ip6e_len + 2) * 4;
1215                         else
1216                                 off += (ext.ip6e_len + 1) * 8;
1217                         proto = ext.ip6e_nxt;
1218                         break;
1219                 case IPPROTO_HOPOPTS:
1220                         if (!pf_pull_hdr(m, off, &ext, sizeof(ext), NULL,
1221                             NULL, AF_INET6))
1222                                 goto shortpkt;
1223                         extoff = off;
1224                         optend = off + (ext.ip6e_len + 1) * 8;
1225                         ooff = off + sizeof(ext);
1226                         do {
1227                                 if (!pf_pull_hdr(m, ooff, &opt.ip6o_type,
1228                                     sizeof(opt.ip6o_type), NULL, NULL,
1229                                     AF_INET6))
1230                                         goto shortpkt;
1231                                 if (opt.ip6o_type == IP6OPT_PAD1) {
1232                                         ooff++;
1233                                         continue;
1234                                 }
1235                                 if (!pf_pull_hdr(m, ooff, &opt, sizeof(opt),
1236                                     NULL, NULL, AF_INET6))
1237                                         goto shortpkt;
1238                                 if (ooff + sizeof(opt) + opt.ip6o_len > optend)
1239                                         goto drop;
1240                                 if (opt.ip6o_type == IP6OPT_JUMBO)
1241                                         goto drop;
1242                                 ooff += sizeof(opt) + opt.ip6o_len;
1243                         } while (ooff < optend);
1244
1245                         off = optend;
1246                         proto = ext.ip6e_nxt;
1247                         break;
1248                 default:
1249                         terminal = 1;
1250                         break;
1251                 }
1252         } while (!terminal);
1253
1254         if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1255                 goto shortpkt;
1256
1257         pf_scrub_ip6(&m, r->min_ttl);
1258
1259         return (PF_PASS);
1260
1261  fragment:
1262         if (sizeof(struct ip6_hdr) + plen > m->m_pkthdr.len)
1263                 goto shortpkt;
1264
1265         if (!pf_pull_hdr(m, off, &frag, sizeof(frag), NULL, NULL, AF_INET6))
1266                 goto shortpkt;
1267
1268         /* Offset now points to data portion. */
1269         off += sizeof(frag);
1270
1271         /* Returns PF_DROP or *m0 is NULL or completely reassembled mbuf. */
1272         if (pf_reassemble6(m0, h, &frag, off, extoff, reason) != PF_PASS)
1273                 return (PF_DROP);
1274         m = *m0;
1275         if (m == NULL)
1276                 return (PF_DROP);
1277
1278         pd->flags |= PFDESC_IP_REAS;
1279         return (PF_PASS);
1280
1281  shortpkt:
1282         REASON_SET(reason, PFRES_SHORT);
1283         if (r != NULL && r->log)
1284                 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1285                     1);
1286         return (PF_DROP);
1287
1288  drop:
1289         REASON_SET(reason, PFRES_NORM);
1290         if (r != NULL && r->log)
1291                 PFLOG_PACKET(kif, m, AF_INET6, dir, *reason, r, NULL, NULL, pd,
1292                     1);
1293         return (PF_DROP);
1294 }
1295 #endif /* INET6 */
1296
1297 int
1298 pf_normalize_tcp(int dir, struct pfi_kif *kif, struct mbuf *m, int ipoff,
1299     int off, void *h, struct pf_pdesc *pd)
1300 {
1301         struct pf_rule  *r, *rm = NULL;
1302         struct tcphdr   *th = pd->hdr.tcp;
1303         int              rewrite = 0;
1304         u_short          reason;
1305         u_int8_t         flags;
1306         sa_family_t      af = pd->af;
1307
1308         PF_RULES_RASSERT();
1309
1310         r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
1311         while (r != NULL) {
1312                 r->evaluations++;
1313                 if (pfi_kif_match(r->kif, kif) == r->ifnot)
1314                         r = r->skip[PF_SKIP_IFP].ptr;
1315                 else if (r->direction && r->direction != dir)
1316                         r = r->skip[PF_SKIP_DIR].ptr;
1317                 else if (r->af && r->af != af)
1318                         r = r->skip[PF_SKIP_AF].ptr;
1319                 else if (r->proto && r->proto != pd->proto)
1320                         r = r->skip[PF_SKIP_PROTO].ptr;
1321                 else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
1322                     r->src.neg, kif, M_GETFIB(m)))
1323                         r = r->skip[PF_SKIP_SRC_ADDR].ptr;
1324                 else if (r->src.port_op && !pf_match_port(r->src.port_op,
1325                             r->src.port[0], r->src.port[1], th->th_sport))
1326                         r = r->skip[PF_SKIP_SRC_PORT].ptr;
1327                 else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
1328                     r->dst.neg, NULL, M_GETFIB(m)))
1329                         r = r->skip[PF_SKIP_DST_ADDR].ptr;
1330                 else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
1331                             r->dst.port[0], r->dst.port[1], th->th_dport))
1332                         r = r->skip[PF_SKIP_DST_PORT].ptr;
1333                 else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
1334                             pf_osfp_fingerprint(pd, m, off, th),
1335                             r->os_fingerprint))
1336                         r = TAILQ_NEXT(r, entries);
1337                 else {
1338                         rm = r;
1339                         break;
1340                 }
1341         }
1342
1343         if (rm == NULL || rm->action == PF_NOSCRUB)
1344                 return (PF_PASS);
1345         else {
1346                 r->packets[dir == PF_OUT]++;
1347                 r->bytes[dir == PF_OUT] += pd->tot_len;
1348         }
1349
1350         if (rm->rule_flag & PFRULE_REASSEMBLE_TCP)
1351                 pd->flags |= PFDESC_TCP_NORM;
1352
1353         flags = th->th_flags;
1354         if (flags & TH_SYN) {
1355                 /* Illegal packet */
1356                 if (flags & TH_RST)
1357                         goto tcp_drop;
1358
1359                 if (flags & TH_FIN)
1360                         goto tcp_drop;
1361         } else {
1362                 /* Illegal packet */
1363                 if (!(flags & (TH_ACK|TH_RST)))
1364                         goto tcp_drop;
1365         }
1366
1367         if (!(flags & TH_ACK)) {
1368                 /* These flags are only valid if ACK is set */
1369                 if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
1370                         goto tcp_drop;
1371         }
1372
1373         /* Check for illegal header length */
1374         if (th->th_off < (sizeof(struct tcphdr) >> 2))
1375                 goto tcp_drop;
1376
1377         /* If flags changed, or reserved data set, then adjust */
1378         if (flags != th->th_flags || th->th_x2 != 0) {
1379                 u_int16_t       ov, nv;
1380
1381                 ov = *(u_int16_t *)(&th->th_ack + 1);
1382                 th->th_flags = flags;
1383                 th->th_x2 = 0;
1384                 nv = *(u_int16_t *)(&th->th_ack + 1);
1385
1386                 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, ov, nv, 0);
1387                 rewrite = 1;
1388         }
1389
1390         /* Remove urgent pointer, if TH_URG is not set */
1391         if (!(flags & TH_URG) && th->th_urp) {
1392                 th->th_sum = pf_proto_cksum_fixup(m, th->th_sum, th->th_urp,
1393                     0, 0);
1394                 th->th_urp = 0;
1395                 rewrite = 1;
1396         }
1397
1398         /* Process options */
1399         if (r->max_mss && pf_normalize_tcpopt(r, m, th, off, pd->af))
1400                 rewrite = 1;
1401
1402         /* copy back packet headers if we sanitized */
1403         if (rewrite)
1404                 m_copyback(m, off, sizeof(*th), (caddr_t)th);
1405
1406         return (PF_PASS);
1407
1408  tcp_drop:
1409         REASON_SET(&reason, PFRES_NORM);
1410         if (rm != NULL && r->log)
1411                 PFLOG_PACKET(kif, m, AF_INET, dir, reason, r, NULL, NULL, pd,
1412                     1);
1413         return (PF_DROP);
1414 }
1415
1416 int
1417 pf_normalize_tcp_init(struct mbuf *m, int off, struct pf_pdesc *pd,
1418     struct tcphdr *th, struct pf_state_peer *src, struct pf_state_peer *dst)
1419 {
1420         u_int32_t tsval, tsecr;
1421         u_int8_t hdr[60];
1422         u_int8_t *opt;
1423
1424         KASSERT((src->scrub == NULL),
1425             ("pf_normalize_tcp_init: src->scrub != NULL"));
1426
1427         src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
1428         if (src->scrub == NULL)
1429                 return (1);
1430
1431         switch (pd->af) {
1432 #ifdef INET
1433         case AF_INET: {
1434                 struct ip *h = mtod(m, struct ip *);
1435                 src->scrub->pfss_ttl = h->ip_ttl;
1436                 break;
1437         }
1438 #endif /* INET */
1439 #ifdef INET6
1440         case AF_INET6: {
1441                 struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1442                 src->scrub->pfss_ttl = h->ip6_hlim;
1443                 break;
1444         }
1445 #endif /* INET6 */
1446         }
1447
1448         /*
1449          * All normalizations below are only begun if we see the start of
1450          * the connections.  They must all set an enabled bit in pfss_flags
1451          */
1452         if ((th->th_flags & TH_SYN) == 0)
1453                 return (0);
1454
1455         if (th->th_off > (sizeof(struct tcphdr) >> 2) && src->scrub &&
1456             pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1457                 /* Diddle with TCP options */
1458                 int hlen;
1459                 opt = hdr + sizeof(struct tcphdr);
1460                 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1461                 while (hlen >= TCPOLEN_TIMESTAMP) {
1462                         switch (*opt) {
1463                         case TCPOPT_EOL:        /* FALLTHROUGH */
1464                         case TCPOPT_NOP:
1465                                 opt++;
1466                                 hlen--;
1467                                 break;
1468                         case TCPOPT_TIMESTAMP:
1469                                 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1470                                         src->scrub->pfss_flags |=
1471                                             PFSS_TIMESTAMP;
1472                                         src->scrub->pfss_ts_mod =
1473                                             htonl(arc4random());
1474
1475                                         /* note PFSS_PAWS not set yet */
1476                                         memcpy(&tsval, &opt[2],
1477                                             sizeof(u_int32_t));
1478                                         memcpy(&tsecr, &opt[6],
1479                                             sizeof(u_int32_t));
1480                                         src->scrub->pfss_tsval0 = ntohl(tsval);
1481                                         src->scrub->pfss_tsval = ntohl(tsval);
1482                                         src->scrub->pfss_tsecr = ntohl(tsecr);
1483                                         getmicrouptime(&src->scrub->pfss_last);
1484                                 }
1485                                 /* FALLTHROUGH */
1486                         default:
1487                                 hlen -= MAX(opt[1], 2);
1488                                 opt += MAX(opt[1], 2);
1489                                 break;
1490                         }
1491                 }
1492         }
1493
1494         return (0);
1495 }
1496
1497 void
1498 pf_normalize_tcp_cleanup(struct pf_state *state)
1499 {
1500         if (state->src.scrub)
1501                 uma_zfree(V_pf_state_scrub_z, state->src.scrub);
1502         if (state->dst.scrub)
1503                 uma_zfree(V_pf_state_scrub_z, state->dst.scrub);
1504
1505         /* Someday... flush the TCP segment reassembly descriptors. */
1506 }
1507
1508 int
1509 pf_normalize_tcp_stateful(struct mbuf *m, int off, struct pf_pdesc *pd,
1510     u_short *reason, struct tcphdr *th, struct pf_state *state,
1511     struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
1512 {
1513         struct timeval uptime;
1514         u_int32_t tsval, tsecr;
1515         u_int tsval_from_last;
1516         u_int8_t hdr[60];
1517         u_int8_t *opt;
1518         int copyback = 0;
1519         int got_ts = 0;
1520
1521         KASSERT((src->scrub || dst->scrub),
1522             ("%s: src->scrub && dst->scrub!", __func__));
1523
1524         /*
1525          * Enforce the minimum TTL seen for this connection.  Negate a common
1526          * technique to evade an intrusion detection system and confuse
1527          * firewall state code.
1528          */
1529         switch (pd->af) {
1530 #ifdef INET
1531         case AF_INET: {
1532                 if (src->scrub) {
1533                         struct ip *h = mtod(m, struct ip *);
1534                         if (h->ip_ttl > src->scrub->pfss_ttl)
1535                                 src->scrub->pfss_ttl = h->ip_ttl;
1536                         h->ip_ttl = src->scrub->pfss_ttl;
1537                 }
1538                 break;
1539         }
1540 #endif /* INET */
1541 #ifdef INET6
1542         case AF_INET6: {
1543                 if (src->scrub) {
1544                         struct ip6_hdr *h = mtod(m, struct ip6_hdr *);
1545                         if (h->ip6_hlim > src->scrub->pfss_ttl)
1546                                 src->scrub->pfss_ttl = h->ip6_hlim;
1547                         h->ip6_hlim = src->scrub->pfss_ttl;
1548                 }
1549                 break;
1550         }
1551 #endif /* INET6 */
1552         }
1553
1554         if (th->th_off > (sizeof(struct tcphdr) >> 2) &&
1555             ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
1556             (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
1557             pf_pull_hdr(m, off, hdr, th->th_off << 2, NULL, NULL, pd->af)) {
1558                 /* Diddle with TCP options */
1559                 int hlen;
1560                 opt = hdr + sizeof(struct tcphdr);
1561                 hlen = (th->th_off << 2) - sizeof(struct tcphdr);
1562                 while (hlen >= TCPOLEN_TIMESTAMP) {
1563                         switch (*opt) {
1564                         case TCPOPT_EOL:        /* FALLTHROUGH */
1565                         case TCPOPT_NOP:
1566                                 opt++;
1567                                 hlen--;
1568                                 break;
1569                         case TCPOPT_TIMESTAMP:
1570                                 /* Modulate the timestamps.  Can be used for
1571                                  * NAT detection, OS uptime determination or
1572                                  * reboot detection.
1573                                  */
1574
1575                                 if (got_ts) {
1576                                         /* Huh?  Multiple timestamps!? */
1577                                         if (V_pf_status.debug >= PF_DEBUG_MISC) {
1578                                                 DPFPRINTF(("multiple TS??\n"));
1579                                                 pf_print_state(state);
1580                                                 printf("\n");
1581                                         }
1582                                         REASON_SET(reason, PFRES_TS);
1583                                         return (PF_DROP);
1584                                 }
1585                                 if (opt[1] >= TCPOLEN_TIMESTAMP) {
1586                                         memcpy(&tsval, &opt[2],
1587                                             sizeof(u_int32_t));
1588                                         if (tsval && src->scrub &&
1589                                             (src->scrub->pfss_flags &
1590                                             PFSS_TIMESTAMP)) {
1591                                                 tsval = ntohl(tsval);
1592                                                 pf_change_proto_a(m, &opt[2],
1593                                                     &th->th_sum,
1594                                                     htonl(tsval +
1595                                                     src->scrub->pfss_ts_mod),
1596                                                     0);
1597                                                 copyback = 1;
1598                                         }
1599
1600                                         /* Modulate TS reply iff valid (!0) */
1601                                         memcpy(&tsecr, &opt[6],
1602                                             sizeof(u_int32_t));
1603                                         if (tsecr && dst->scrub &&
1604                                             (dst->scrub->pfss_flags &
1605                                             PFSS_TIMESTAMP)) {
1606                                                 tsecr = ntohl(tsecr)
1607                                                     - dst->scrub->pfss_ts_mod;
1608                                                 pf_change_proto_a(m, &opt[6],
1609                                                     &th->th_sum, htonl(tsecr),
1610                                                     0);
1611                                                 copyback = 1;
1612                                         }
1613                                         got_ts = 1;
1614                                 }
1615                                 /* FALLTHROUGH */
1616                         default:
1617                                 hlen -= MAX(opt[1], 2);
1618                                 opt += MAX(opt[1], 2);
1619                                 break;
1620                         }
1621                 }
1622                 if (copyback) {
1623                         /* Copyback the options, caller copys back header */
1624                         *writeback = 1;
1625                         m_copyback(m, off + sizeof(struct tcphdr),
1626                             (th->th_off << 2) - sizeof(struct tcphdr), hdr +
1627                             sizeof(struct tcphdr));
1628                 }
1629         }
1630
1631         /*
1632          * Must invalidate PAWS checks on connections idle for too long.
1633          * The fastest allowed timestamp clock is 1ms.  That turns out to
1634          * be about 24 days before it wraps.  XXX Right now our lowerbound
1635          * TS echo check only works for the first 12 days of a connection
1636          * when the TS has exhausted half its 32bit space
1637          */
1638 #define TS_MAX_IDLE     (24*24*60*60)
1639 #define TS_MAX_CONN     (12*24*60*60)   /* XXX remove when better tsecr check */
1640
1641         getmicrouptime(&uptime);
1642         if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
1643             (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
1644             time_uptime - state->creation > TS_MAX_CONN))  {
1645                 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1646                         DPFPRINTF(("src idled out of PAWS\n"));
1647                         pf_print_state(state);
1648                         printf("\n");
1649                 }
1650                 src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
1651                     | PFSS_PAWS_IDLED;
1652         }
1653         if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
1654             uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
1655                 if (V_pf_status.debug >= PF_DEBUG_MISC) {
1656                         DPFPRINTF(("dst idled out of PAWS\n"));
1657                         pf_print_state(state);
1658                         printf("\n");
1659                 }
1660                 dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
1661                     | PFSS_PAWS_IDLED;
1662         }
1663
1664         if (got_ts && src->scrub && dst->scrub &&
1665             (src->scrub->pfss_flags & PFSS_PAWS) &&
1666             (dst->scrub->pfss_flags & PFSS_PAWS)) {
1667                 /* Validate that the timestamps are "in-window".
1668                  * RFC1323 describes TCP Timestamp options that allow
1669                  * measurement of RTT (round trip time) and PAWS
1670                  * (protection against wrapped sequence numbers).  PAWS
1671                  * gives us a set of rules for rejecting packets on
1672                  * long fat pipes (packets that were somehow delayed
1673                  * in transit longer than the time it took to send the
1674                  * full TCP sequence space of 4Gb).  We can use these
1675                  * rules and infer a few others that will let us treat
1676                  * the 32bit timestamp and the 32bit echoed timestamp
1677                  * as sequence numbers to prevent a blind attacker from
1678                  * inserting packets into a connection.
1679                  *
1680                  * RFC1323 tells us:
1681                  *  - The timestamp on this packet must be greater than
1682                  *    or equal to the last value echoed by the other
1683                  *    endpoint.  The RFC says those will be discarded
1684                  *    since it is a dup that has already been acked.
1685                  *    This gives us a lowerbound on the timestamp.
1686                  *        timestamp >= other last echoed timestamp
1687                  *  - The timestamp will be less than or equal to
1688                  *    the last timestamp plus the time between the
1689                  *    last packet and now.  The RFC defines the max
1690                  *    clock rate as 1ms.  We will allow clocks to be
1691                  *    up to 10% fast and will allow a total difference
1692                  *    or 30 seconds due to a route change.  And this
1693                  *    gives us an upperbound on the timestamp.
1694                  *        timestamp <= last timestamp + max ticks
1695                  *    We have to be careful here.  Windows will send an
1696                  *    initial timestamp of zero and then initialize it
1697                  *    to a random value after the 3whs; presumably to
1698                  *    avoid a DoS by having to call an expensive RNG
1699                  *    during a SYN flood.  Proof MS has at least one
1700                  *    good security geek.
1701                  *
1702                  *  - The TCP timestamp option must also echo the other
1703                  *    endpoints timestamp.  The timestamp echoed is the
1704                  *    one carried on the earliest unacknowledged segment
1705                  *    on the left edge of the sequence window.  The RFC
1706                  *    states that the host will reject any echoed
1707                  *    timestamps that were larger than any ever sent.
1708                  *    This gives us an upperbound on the TS echo.
1709                  *        tescr <= largest_tsval
1710                  *  - The lowerbound on the TS echo is a little more
1711                  *    tricky to determine.  The other endpoint's echoed
1712                  *    values will not decrease.  But there may be
1713                  *    network conditions that re-order packets and
1714                  *    cause our view of them to decrease.  For now the
1715                  *    only lowerbound we can safely determine is that
1716                  *    the TS echo will never be less than the original
1717                  *    TS.  XXX There is probably a better lowerbound.
1718                  *    Remove TS_MAX_CONN with better lowerbound check.
1719                  *        tescr >= other original TS
1720                  *
1721                  * It is also important to note that the fastest
1722                  * timestamp clock of 1ms will wrap its 32bit space in
1723                  * 24 days.  So we just disable TS checking after 24
1724                  * days of idle time.  We actually must use a 12d
1725                  * connection limit until we can come up with a better
1726                  * lowerbound to the TS echo check.
1727                  */
1728                 struct timeval delta_ts;
1729                 int ts_fudge;
1730
1731                 /*
1732                  * PFTM_TS_DIFF is how many seconds of leeway to allow
1733                  * a host's timestamp.  This can happen if the previous
1734                  * packet got delayed in transit for much longer than
1735                  * this packet.
1736                  */
1737                 if ((ts_fudge = state->rule.ptr->timeout[PFTM_TS_DIFF]) == 0)
1738                         ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF];
1739
1740                 /* Calculate max ticks since the last timestamp */
1741 #define TS_MAXFREQ      1100            /* RFC max TS freq of 1Khz + 10% skew */
1742 #define TS_MICROSECS    1000000         /* microseconds per second */
1743                 delta_ts = uptime;
1744                 timevalsub(&delta_ts, &src->scrub->pfss_last);
1745                 tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
1746                 tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);
1747
1748                 if ((src->state >= TCPS_ESTABLISHED &&
1749                     dst->state >= TCPS_ESTABLISHED) &&
1750                     (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
1751                     SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
1752                     (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
1753                     SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
1754                         /* Bad RFC1323 implementation or an insertion attack.
1755                          *
1756                          * - Solaris 2.6 and 2.7 are known to send another ACK
1757                          *   after the FIN,FIN|ACK,ACK closing that carries
1758                          *   an old timestamp.
1759                          */
1760
1761                         DPFPRINTF(("Timestamp failed %c%c%c%c\n",
1762                             SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
1763                             SEQ_GT(tsval, src->scrub->pfss_tsval +
1764                             tsval_from_last) ? '1' : ' ',
1765                             SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
1766                             SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' '));
1767                         DPFPRINTF((" tsval: %u  tsecr: %u  +ticks: %u  "
1768                             "idle: %jus %lums\n",
1769                             tsval, tsecr, tsval_from_last,
1770                             (uintmax_t)delta_ts.tv_sec,
1771                             delta_ts.tv_usec / 1000));
1772                         DPFPRINTF((" src->tsval: %u  tsecr: %u\n",
1773                             src->scrub->pfss_tsval, src->scrub->pfss_tsecr));
1774                         DPFPRINTF((" dst->tsval: %u  tsecr: %u  tsval0: %u"
1775                             "\n", dst->scrub->pfss_tsval,
1776                             dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0));
1777                         if (V_pf_status.debug >= PF_DEBUG_MISC) {
1778                                 pf_print_state(state);
1779                                 pf_print_flags(th->th_flags);
1780                                 printf("\n");
1781                         }
1782                         REASON_SET(reason, PFRES_TS);
1783                         return (PF_DROP);
1784                 }
1785
1786                 /* XXX I'd really like to require tsecr but it's optional */
1787
1788         } else if (!got_ts && (th->th_flags & TH_RST) == 0 &&
1789             ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
1790             || pd->p_len > 0 || (th->th_flags & TH_SYN)) &&
1791             src->scrub && dst->scrub &&
1792             (src->scrub->pfss_flags & PFSS_PAWS) &&
1793             (dst->scrub->pfss_flags & PFSS_PAWS)) {
1794                 /* Didn't send a timestamp.  Timestamps aren't really useful
1795                  * when:
1796                  *  - connection opening or closing (often not even sent).
1797                  *    but we must not let an attacker to put a FIN on a
1798                  *    data packet to sneak it through our ESTABLISHED check.
1799                  *  - on a TCP reset.  RFC suggests not even looking at TS.
1800                  *  - on an empty ACK.  The TS will not be echoed so it will
1801                  *    probably not help keep the RTT calculation in sync and
1802                  *    there isn't as much danger when the sequence numbers
1803                  *    got wrapped.  So some stacks don't include TS on empty
1804                  *    ACKs :-(
1805                  *
1806                  * To minimize the disruption to mostly RFC1323 conformant
1807                  * stacks, we will only require timestamps on data packets.
1808                  *
1809                  * And what do ya know, we cannot require timestamps on data
1810                  * packets.  There appear to be devices that do legitimate
1811                  * TCP connection hijacking.  There are HTTP devices that allow
1812                  * a 3whs (with timestamps) and then buffer the HTTP request.
1813                  * If the intermediate device has the HTTP response cache, it
1814                  * will spoof the response but not bother timestamping its
1815                  * packets.  So we can look for the presence of a timestamp in
1816                  * the first data packet and if there, require it in all future
1817                  * packets.
1818                  */
1819
1820                 if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
1821                         /*
1822                          * Hey!  Someone tried to sneak a packet in.  Or the
1823                          * stack changed its RFC1323 behavior?!?!
1824                          */
1825                         if (V_pf_status.debug >= PF_DEBUG_MISC) {
1826                                 DPFPRINTF(("Did not receive expected RFC1323 "
1827                                     "timestamp\n"));
1828                                 pf_print_state(state);
1829                                 pf_print_flags(th->th_flags);
1830                                 printf("\n");
1831                         }
1832                         REASON_SET(reason, PFRES_TS);
1833                         return (PF_DROP);
1834                 }
1835         }
1836
1837         /*
1838          * We will note if a host sends his data packets with or without
1839          * timestamps.  And require all data packets to contain a timestamp
1840          * if the first does.  PAWS implicitly requires that all data packets be
1841          * timestamped.  But I think there are middle-man devices that hijack
1842          * TCP streams immediately after the 3whs and don't timestamp their
1843          * packets (seen in a WWW accelerator or cache).
1844          */
1845         if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
1846             (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
1847                 if (got_ts)
1848                         src->scrub->pfss_flags |= PFSS_DATA_TS;
1849                 else {
1850                         src->scrub->pfss_flags |= PFSS_DATA_NOTS;
1851                         if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
1852                             (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
1853                                 /* Don't warn if other host rejected RFC1323 */
1854                                 DPFPRINTF(("Broken RFC1323 stack did not "
1855                                     "timestamp data packet. Disabled PAWS "
1856                                     "security.\n"));
1857                                 pf_print_state(state);
1858                                 pf_print_flags(th->th_flags);
1859                                 printf("\n");
1860                         }
1861                 }
1862         }
1863
1864         /*
1865          * Update PAWS values
1866          */
1867         if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
1868             (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
1869                 getmicrouptime(&src->scrub->pfss_last);
1870                 if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
1871                     (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1872                         src->scrub->pfss_tsval = tsval;
1873
1874                 if (tsecr) {
1875                         if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
1876                             (src->scrub->pfss_flags & PFSS_PAWS) == 0)
1877                                 src->scrub->pfss_tsecr = tsecr;
1878
1879                         if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
1880                             (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
1881                             src->scrub->pfss_tsval0 == 0)) {
1882                                 /* tsval0 MUST be the lowest timestamp */
1883                                 src->scrub->pfss_tsval0 = tsval;
1884                         }
1885
1886                         /* Only fully initialized after a TS gets echoed */
1887                         if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
1888                                 src->scrub->pfss_flags |= PFSS_PAWS;
1889                 }
1890         }
1891
1892         /* I have a dream....  TCP segment reassembly.... */
1893         return (0);
1894 }
1895
1896 static int
1897 pf_normalize_tcpopt(struct pf_rule *r, struct mbuf *m, struct tcphdr *th,
1898     int off, sa_family_t af)
1899 {
1900         u_int16_t       *mss;
1901         int              thoff;
1902         int              opt, cnt, optlen = 0;
1903         int              rewrite = 0;
1904         u_char           opts[TCP_MAXOLEN];
1905         u_char          *optp = opts;
1906
1907         thoff = th->th_off << 2;
1908         cnt = thoff - sizeof(struct tcphdr);
1909
1910         if (cnt > 0 && !pf_pull_hdr(m, off + sizeof(*th), opts, cnt,
1911             NULL, NULL, af))
1912                 return (rewrite);
1913
1914         for (; cnt > 0; cnt -= optlen, optp += optlen) {
1915                 opt = optp[0];
1916                 if (opt == TCPOPT_EOL)
1917                         break;
1918                 if (opt == TCPOPT_NOP)
1919                         optlen = 1;
1920                 else {
1921                         if (cnt < 2)
1922                                 break;
1923                         optlen = optp[1];
1924                         if (optlen < 2 || optlen > cnt)
1925                                 break;
1926                 }
1927                 switch (opt) {
1928                 case TCPOPT_MAXSEG:
1929                         mss = (u_int16_t *)(optp + 2);
1930                         if ((ntohs(*mss)) > r->max_mss) {
1931                                 th->th_sum = pf_proto_cksum_fixup(m,
1932                                     th->th_sum, *mss, htons(r->max_mss), 0);
1933                                 *mss = htons(r->max_mss);
1934                                 rewrite = 1;
1935                         }
1936                         break;
1937                 default:
1938                         break;
1939                 }
1940         }
1941
1942         if (rewrite)
1943                 m_copyback(m, off + sizeof(*th), thoff - sizeof(*th), opts);
1944
1945         return (rewrite);
1946 }
1947
1948 #ifdef INET
1949 static void
1950 pf_scrub_ip(struct mbuf **m0, u_int32_t flags, u_int8_t min_ttl, u_int8_t tos)
1951 {
1952         struct mbuf             *m = *m0;
1953         struct ip               *h = mtod(m, struct ip *);
1954
1955         /* Clear IP_DF if no-df was requested */
1956         if (flags & PFRULE_NODF && h->ip_off & htons(IP_DF)) {
1957                 u_int16_t ip_off = h->ip_off;
1958
1959                 h->ip_off &= htons(~IP_DF);
1960                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
1961         }
1962
1963         /* Enforce a minimum ttl, may cause endless packet loops */
1964         if (min_ttl && h->ip_ttl < min_ttl) {
1965                 u_int16_t ip_ttl = h->ip_ttl;
1966
1967                 h->ip_ttl = min_ttl;
1968                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
1969         }
1970
1971         /* Enforce tos */
1972         if (flags & PFRULE_SET_TOS) {
1973                 u_int16_t       ov, nv;
1974
1975                 ov = *(u_int16_t *)h;
1976                 h->ip_tos = tos | (h->ip_tos & IPTOS_ECN_MASK);
1977                 nv = *(u_int16_t *)h;
1978
1979                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
1980         }
1981
1982         /* random-id, but not for fragments */
1983         if (flags & PFRULE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) {
1984                 uint16_t ip_id = h->ip_id;
1985
1986                 ip_fillid(h);
1987                 h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
1988         }
1989 }
1990 #endif /* INET */
1991
1992 #ifdef INET6
1993 static void
1994 pf_scrub_ip6(struct mbuf **m0, u_int8_t min_ttl)
1995 {
1996         struct mbuf             *m = *m0;
1997         struct ip6_hdr          *h = mtod(m, struct ip6_hdr *);
1998
1999         /* Enforce a minimum ttl, may cause endless packet loops */
2000         if (min_ttl && h->ip6_hlim < min_ttl)
2001                 h->ip6_hlim = min_ttl;
2002 }
2003 #endif